This invention relates to packages made from flexible film material, and more particularly, to bag-packages of kinds suitable for coffee and other foodstuffs which require gas or moisture protection and are commonly packaged under vacuum.
Certain products, such as coffee, have heretofore been marketed in flexible packages so-called "soft packs". One such kind of package consists of a bag constructed from a laminated film material of multiple plies, the material providing physical containment for the product as well as a moisture and gas barrier. Numerous film materials have been used, but typically, the materials include one or more plies for physical strength, dimensional stability, and gas and moisture barriers; a ply which is or can be printed upon to provide for labeling and other markings; and a ply which provides a sealant.
For some applications, it is advantageous to construct the film material and the package in an in-line process, by heat sealing the laminated material. The package may be filled and closed to produce a unit ready for shipping. Packages or bags of the above description may be used in vacuum packing, a familiar technique in which the contents are exposed to a reduced atmosphere during or just prior to a closing operation to draw off atmospheric air or other gases (which may contribute to spoilage) or to eliminate gases which might otherwise evolve or diffuse out of the packaged product over time. One such package is described in U.S. Pat. No. 4,488,647, issued Dec. 18, 1984, to John S. Davis, and assigned to the assignee of the present invention and application.
In instances in which the contents of the container are granular in character, such as most typically, ground coffee, the application of vacuum causes the film of the bag to conform to the surface of the material, and to thus take on a rough, grainy contour and appearance. In some circumstances, such an appearance is considered undesirable, and conventional practice has been to apply to the vacuum container a smooth over-wrap. Because the over-wrap, unlike the underlying bag, is not subjected to vacuum, the surface of the over-wrap has a smooth outer surface.
U.S. Pat. No. 4,734,292, issued Mar. 29, 1988, to Gerardus Van Boxtel, discloses a method of making a smooth-surfaced vacuum package in which the package includes inner and outer bags, separated by a gas space. The outer bag is made gas-impermeable and sealable, to isolate the gas space from the ambient atmosphere. In this apparatus and method, the inner bag is first heat sealed to seal the product within it under vacuum, and a gas is thereafter introduced into the space between the bags. The outer bag is made gas-impermeable, but the inner bag is made of a semipermeable material, so that the gas in the gas space and any gas eventually evolved from the product cause the wall of the outer bag to remain smooth.
Another method for forming a smooth-walled package is shown in U.S. Pat. No. 4,727,706, issued Mar. 1, 1988 to Jeffrey S. Beer.